Displays deeply nested comments inline.

This just puts them in three traversal order rather than chronological order.
Not sure which makes the most sense, but I'll implement both ways.

lms/static/coffee/src/discussion/views/thread_response_view.coffee

@@ -34,6 +34,9 @@ if Backbone?
       view = new ResponseCommentView(model: comment)
       view.render()
       @$el.find(".comments li:last").before(view.el)
+      children = new Comments(comment.get('children'))
+      children.each @renderComment
+
 
     toggleVote: (event) ->
       event.preventDefault()